1. Field of the Invention
The present invention relates to an image forming method which forms a toner image of full color by performing a transfer process using supersonic oscillation, in particular, relates to an image forming method which performs the transfer process by supersonic oscillation using an oilless toner which has specific grain size distribution, or a toner with which the form and the particle size are specified.
2. Related Art
Recently, digital method becomes as the main stream of the image formation by the electrophotographic system. One of such the trends of the technology is a technology of full color image formation. One of the techniques to accelerate the colorization of the toner image is a full color image forming method employing an oil less toner containing a large amount of a parting agent in the toner particle (cf. Japanese Patent Publication Open to Public Inspection, hereinafter referred to as Japanese Patent O.P.I. Publication, No. 2002-214821, paragraph 0049).
In digital image formation, since a dot picture image with a small 1200 dpi (dot number per inch, one inch is 2.54 cm) level may be visualized, when performing image formation, toner so called a small diameter toner whose particle size is several micron orders is used preferably.
Incidentally, in such the image formation employing the small diameter toner, the transfer ability becomes worse on the occasion of transfer of the image formed on the photoreceptor onto an image receiving material such as paper and OHP film. Especially, in an image formation of full color which superimposes the color toners of Y, M, and C so as to form a toner image, the tendency appears significantly, It was difficult to transfer a toner image stably and certainly on a transfer material from a photoreceptor surface or an intermediate transfer member, and also it was difficult to produce a full color picture image which has a good color balance and optical density.
Therefore, techniques have been investigated for surely transferring a toner image onto an image receiving material by applying a physical action to a photoreceptor, as the one measure, there was a method that when transferring a toner image on a transfer material, a supersonic wave was irradiated at a bearing body which bears a toner image, and a toner image was made to transfer efficiently on a transfer material from the bearing body surface in the action of the oscillation by a supersonic wave, (cf. for example, Japanese Patent O.P.I. Publication Nos. 2002-100546, paragraph 0052-0061 and 2001-117381, paragraph 0035 and 0062).
However, the toner transfer methods employing ultrasonic waves disclosed in Japanese Patent O.P.I. Publication Nos. 2002-100546 and 2001-117381 are methods which have been developed for toner which is employed while coating oil on an image receiving material on the occasion of fixing. And although the transfer using supersonic oscillation was tried with an oilless toner having a releasing agent, it did not go well at all in whether fill the performance for which present invention persons ask. When oilless toner was used, the releasing agent was detached from toner particles under the influence of the oscillation by a supersonic wave, and in a fixing process, a transfer material coiled around a fusing roller, and offset was generated.
Moreover, since, as for an oilless toner with which the releasing agent detached itself, an external additive agent also detaches itself with a releasing agent, an adhesion force of the oilless tone with a photoreceptor increases, toner particles with which the transfer rate fell were generated. Therefore, a toner image will become easy to be disordered if the oscillation by a supersonic wave is received, and as a result, there are problems that the color reproduction quality in a full color picture image falls, the toner image of each color do not superimpose well, and picture image scattering is generated.
The invention is accomplished according to the above situation. The object of the invention is to provide an image forming method without occurrence of the winding the image receiving material about the fixing roller and the offset by employing a toner from which the parting agent is not released when the ultrasonic waves are applied.
The invention is to provide an image forming method in which the toner image is not deformed even when the vibration of the ultrasonic waves are applied and the toner images can be exactly overlapped to form a full color image.